1. Field of the Invention
The invention relates to a method for the manufacture of an electrochemical cell or battery, for example a fuel cell or fuel-cell battery, consisting of a stack of plate-shaped elements, including at least two electrode elements, each of which consists of a sheet or plate of electrode material which is mounted in a frame made of electrically insulating fibrous-web material impregnated with a thermosetting synthetic material, which elements, prior to setting, are stacked to form package of the desired composition in such a way that gas or liquid chambers are formed between the elements, after which the stack is subjected to a compression molding operation at a temperature causing the thermosetting synthetic material to polymerize, thus forming the stack into a coherent block.
2. Description of the Prior Art
One prior art method is described in Dutch Pat. application No. 75 09675, laid open for inspection. According to this known method, a fibrous web containing non-polymerized thermosetting synthetic material is stuck onto one side or both sides of a band of electrode material at a temperature at which the thermosetting synthetic material is adhesive but does not yet polymerize. The bands thus obtained are cut into plate-shaped elements which are stacked to form a package of the desired composition, while in most cases strips, not adhering to the synthetic material, are placed between the elements in order to form the channels which are required in the finished cell or battery,. Subsequently, the stacked package is for a certain time at a certain pressure exposed to a temperature at which the thermosetting synthetic material polymerizes. The flowing of the synthetic material causes the sheets of electrode material to be bonded to the frames, while the frames are bonded to each other as well, so that the stack is formed into a coherent block. Next, the strips are pulled out of the channels which have been formed, and the open ends of the channels at the outside of the block are sealed off.
It has been found that electrochemical cells or batteries manufactured according to this known method may exhibit the undesirable phenomenon of decreased cell performance after manufacture resulting from the improper bonding of the sheets or plates or electrode material in the finished block which is not sufficiently impermeable to gas or liquid, so that leakage may occur between the various gas or liquid chambers, which of course seriously interferes with proper functioning of the cell or battery. Inferior bonding may also occur along the edges of the channels which have been formed by means of strips. This imperfect bonding is believed to be attributable to the fact that the heating of the rather thick stacked package proceeds so slowly that the temperature at which the non-polymerized synthetic material would flow sufficiently to effect proper bonding is locally reached only when the polymerization (setting) of the thermosetting synthetic material has advanced so far already that the material can no longer flow sufficiently. The purpose of the invention is to provide a method which does not have this drawback.